1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
|
//===--- PartiallyInlineLibCalls.cpp - Partially inline libcalls ----------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This pass tries to partially inline the fast path of well-known library
// functions, such as using square-root instructions for cases where sqrt()
// does not need to set errno.
//
//===----------------------------------------------------------------------===//
#include "llvm/Transforms/Scalar/PartiallyInlineLibCalls.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/IRBuilder.h"
#include "llvm/Support/DebugCounter.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
using namespace llvm;
#define DEBUG_TYPE "partially-inline-libcalls"
DEBUG_COUNTER(PILCounter, "partially-inline-libcalls-transform",
"Controls transformations in partially-inline-libcalls");
static bool optimizeSQRT(CallInst *Call, Function *CalledFunc,
BasicBlock &CurrBB, Function::iterator &BB,
const TargetTransformInfo *TTI) {
// There is no need to change the IR, since backend will emit sqrt
// instruction if the call has already been marked read-only.
if (Call->onlyReadsMemory())
return false;
if (!DebugCounter::shouldExecute(PILCounter))
return false;
// Do the following transformation:
//
// (before)
// dst = sqrt(src)
//
// (after)
// v0 = sqrt_noreadmem(src) # native sqrt instruction.
// [if (v0 is a NaN) || if (src < 0)]
// v1 = sqrt(src) # library call.
// dst = phi(v0, v1)
//
// Move all instructions following Call to newly created block JoinBB.
// Create phi and replace all uses.
BasicBlock *JoinBB = llvm::SplitBlock(&CurrBB, Call->getNextNode());
IRBuilder<> Builder(JoinBB, JoinBB->begin());
Type *Ty = Call->getType();
PHINode *Phi = Builder.CreatePHI(Ty, 2);
Call->replaceAllUsesWith(Phi);
// Create basic block LibCallBB and insert a call to library function sqrt.
BasicBlock *LibCallBB = BasicBlock::Create(CurrBB.getContext(), "call.sqrt",
CurrBB.getParent(), JoinBB);
Builder.SetInsertPoint(LibCallBB);
Instruction *LibCall = Call->clone();
Builder.Insert(LibCall);
Builder.CreateBr(JoinBB);
// Add attribute "readnone" so that backend can use a native sqrt instruction
// for this call. Insert a FP compare instruction and a conditional branch
// at the end of CurrBB.
Call->addAttribute(AttributeList::FunctionIndex, Attribute::ReadNone);
CurrBB.getTerminator()->eraseFromParent();
Builder.SetInsertPoint(&CurrBB);
Value *FCmp = TTI->isFCmpOrdCheaperThanFCmpZero(Ty)
? Builder.CreateFCmpORD(Call, Call)
: Builder.CreateFCmpOGE(Call->getOperand(0),
ConstantFP::get(Ty, 0.0));
Builder.CreateCondBr(FCmp, JoinBB, LibCallBB);
// Add phi operands.
Phi->addIncoming(Call, &CurrBB);
Phi->addIncoming(LibCall, LibCallBB);
BB = JoinBB->getIterator();
return true;
}
static bool runPartiallyInlineLibCalls(Function &F, TargetLibraryInfo *TLI,
const TargetTransformInfo *TTI) {
bool Changed = false;
Function::iterator CurrBB;
for (Function::iterator BB = F.begin(), BE = F.end(); BB != BE;) {
CurrBB = BB++;
for (BasicBlock::iterator II = CurrBB->begin(), IE = CurrBB->end();
II != IE; ++II) {
CallInst *Call = dyn_cast<CallInst>(&*II);
Function *CalledFunc;
if (!Call || !(CalledFunc = Call->getCalledFunction()))
continue;
if (Call->isNoBuiltin())
continue;
// Skip if function either has local linkage or is not a known library
// function.
LibFunc LF;
if (CalledFunc->hasLocalLinkage() ||
!TLI->getLibFunc(*CalledFunc, LF) || !TLI->has(LF))
continue;
switch (LF) {
case LibFunc_sqrtf:
case LibFunc_sqrt:
if (TTI->haveFastSqrt(Call->getType()) &&
optimizeSQRT(Call, CalledFunc, *CurrBB, BB, TTI))
break;
continue;
default:
continue;
}
Changed = true;
break;
}
}
return Changed;
}
PreservedAnalyses
PartiallyInlineLibCallsPass::run(Function &F, FunctionAnalysisManager &AM) {
auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
auto &TTI = AM.getResult<TargetIRAnalysis>(F);
if (!runPartiallyInlineLibCalls(F, &TLI, &TTI))
return PreservedAnalyses::all();
return PreservedAnalyses::none();
}
namespace {
class PartiallyInlineLibCallsLegacyPass : public FunctionPass {
public:
static char ID;
PartiallyInlineLibCallsLegacyPass() : FunctionPass(ID) {
initializePartiallyInlineLibCallsLegacyPassPass(
*PassRegistry::getPassRegistry());
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.addRequired<TargetLibraryInfoWrapperPass>();
AU.addRequired<TargetTransformInfoWrapperPass>();
FunctionPass::getAnalysisUsage(AU);
}
bool runOnFunction(Function &F) override {
if (skipFunction(F))
return false;
TargetLibraryInfo *TLI =
&getAnalysis<TargetLibraryInfoWrapperPass>().getTLI();
const TargetTransformInfo *TTI =
&getAnalysis<TargetTransformInfoWrapperPass>().getTTI(F);
return runPartiallyInlineLibCalls(F, TLI, TTI);
}
};
}
char PartiallyInlineLibCallsLegacyPass::ID = 0;
INITIALIZE_PASS_BEGIN(PartiallyInlineLibCallsLegacyPass,
"partially-inline-libcalls",
"Partially inline calls to library functions", false,
false)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
INITIALIZE_PASS_END(PartiallyInlineLibCallsLegacyPass,
"partially-inline-libcalls",
"Partially inline calls to library functions", false, false)
FunctionPass *llvm::createPartiallyInlineLibCallsPass() {
return new PartiallyInlineLibCallsLegacyPass();
}
|
